Cut hens in half, season with salt and pepper. Melt butter or margarine in large skillet using medium heat. Add hens, skin side down and saute until golden brown. Turn, add onion and brown other side. Drain mushrooms (save liquid) and add the liquid and chicken broth to hens. Simmer, cover, and cook on low heat for 45 minutes. Remove hens and place on warm serving dish. Combine cornstarch, water and Kitchen Bouquet. Stir this mixture into skillet drippings. Cook, stirring constantly, until gravy thickens and is smooth. Switch to low heat and stir in sour cream and mushrooms. Heat but do not boil. Serve sauce in gravy boat or pour over hens. May substitute chicken breasts or thighs for the hens.